Catalytic ammoxidation of olefins to nitriles



United States Patent O US. Cl. 260465.3 Claims ABSTRACT OF THEDISCLOSURE A catalyst consisting essentially of cerium tellurite, and aprocess for the preparation of unsaturated nitriles by reacting anolefin, ammonia and oxygen in the presence of such catalyst.

BACKGROUND OF THE INVENTION The present invention relates to catalystsand to a catalytic process for the production of nitriles, moreparticularly the invention relates to an improved process for theproduction of acrylonitrile and to particular catalysts for use in suchprocess.

Processes are known in which an olefin is reacted with ammonia andoxygen in the presence of specific catalysts to obtain unsaturatednitriles.

The known catalysts include several elements in the form of acids orsalts as for example, molybdic acid, phosphomolybdic acid andphosphotungstic acid; phosphoric acids activated by several elements,bismuth compounds, phosphorus, oxygen, vanadium and other elements.

Most of such processes do not afford however, fully satisfactoryresults. They exhibit a number of drawbacks as relatively lowselectively i.e. a low yield of the desired unsaturated nitrile which isobtained, together with great quantities of by-products and carbonoxides.

Said by-products give rise to a lose in starting material and makedifiicult the recovery of the desired unsaturated nitrile in pure state.

Other drawbacks of the known processes are, generally, the lowconversion of reactants and the necessity of using long contact timeswhich consequently involve low productivity of the catalyst.

Said drawbacks can be overcome through the process of this inveniton,which process concerns the producti n of unsaturated aliphatic nitrilesobtained through the reaction of an olefin with oxygen and ammonia. Theprocess in accordance with this invention is carried out in the presenceof catalysts alfording high yields of unsaturated nitriles and highconversions of the reactants with relatively short contact times.

Furthermore, the catalysts according to this invention have a long lifewithout exhibiting any decrease in their catalytic activity and withoutrequiring any reactivation.

THE INVENTION Therefore, an object of this invention is to provide ational type, and can be used either in fixed or fluid bed.

CeTe O can, as known, be prepared by intimately mixing TeO with CeOfinely powdered, in the molar ratio 3:1, and carrying out a reaction insolid phase in preferably in an oxidizing atmosphere, at a temperaturecomprised from between 600 C. and 700 C. and a reaction time rangingfrom 2 to 30 hours.

The process object of this invention may be applied to propylene, inorder to yield acryl-onitrile, and to isobutene in order to obtainrnethacrylonitrile.

In this process it is preferable to use pure olefin, but it has alsobeen found that the process can take place in the presence of paraffinichydrocarbons inert to the process conditions, which act as diluents.

The oxygen necessary for the reaction can be fed, as such, or as anoxygen containing gas, as, for example, air. This latter may be moreconvenient either for strictly economic reasons or for the presence ofnitrogen which accompanies the same and which acts as an inert diluentable to moderate the exothermic characteristics of the reaction.

The amount of oxygen or of the gas containing oxygen which may be usedwith respect to the olefin may vary within wide limits. The molar ratiooxygen: olefin is preferably comprised between about 1:1 and about 3:1.

Ammonia is used in quantities that may also vary within wide limits withrespect to olefin. The molar ratio ammonia: olefin is, however,preferably comprised between about 06:1 and about 2:1. The highselectivity of the catalysts of this invention permits an almost totalexploitation of the ammonia so that only a slight excess of ammonia withrespect to the olefin is necessary in the reaction medium.

Atmospheric pressure is quite suflicient for conducting the reaction butthe reaction can also be carried out at superatmospheric pressures.

The reaction temperature may be comprised Within 330 C. and 550 C. buttemperatures within 380 C. and 500 C. are preferable, since they permithigh conversions under relatively short contact times, as the followingexamples will better illustrate.

The contact times may vary within wide limits, for example from 0.1 upto 20 seconds, but it has been found that, owing to the high activity ofthe catalyst, contact times lower than one second are generally enoughto afford high conversions of reactants, so that the preferred contacttime ranges between 0.5 and 15 seconds. The catalysts according to thisinvention, when in association with a carrier, are prepared with a ratioactive part: carrier variable within 15-50% by weight of active part,calculated as the sum of the oxides at the maximum valency and %50% byweight of carrier.

Several'substances, silica, alumina, alundum, fireclays and the like,may be used as a carrier, either in the form of suitably granulatedpowder or as granules, as well as gels of silica or alumina.

The results achieved by using a carrier made of commercialmicrospheroidal macroporous silica proved to be particularly suitable.

When it is desired to operate with said suitably supported catalysts,according to an embodiment of this in- 3 vention, the impregnation ofthe carrier with the active part is performed as follows:

Cerous nitrate Ce(NO -6H O and telluric acid H TeO -2H O are dissolvedin water and in concentrated nitric acid.

The silica impregnated in this way was heated at 620 C. in the presenceof air, for 8 hours: after this treatment Te and Ce oxides wereconverted into CeTe O in a substantially quantitative extent.

The product obtained was used for the ammoxidation The terms herein usedhave the following meaning:

percent conversion of the olefin:

mole of reacted olefin mole of olefin fed X100 Net yield orselectivity=percent yield of product X with reference to the convertedolefin:

weight of carbon in product X weight of carbon in the converted olefinGross yield=percent yield of product X witli respect to the fed olefin:

weight of carbon in product X X100 weight of carbon in the olefin fedcontact time: the time during which a unit volume of the gaseous mixturefed, measured under the average temperature and pressure conditions inthe reactor, remains in contact with the apparent unit volume of I thecatalyst.

EXAMPLE 1 The solution thus obtained is used for the impregnationreaction of the olefin'appearing in the following exot' the silica whichconstituted the carrier after its volume amples. has been rectified byadding water in such a quantity to EXAMPLE 2 make it equal to the volumeof the pores of the silica to be impregnated, 10 4.5 cc. equal to 2.7 g.of a catalyst prepared according The impregnation is carried out byslowly pouring the to Example 1' were put into a microreactorconstituted solution on the silica while kept under stirring. The imy aStainless Ste l pipe suitably heated to form a fixed pregnated silica isstirred for about one hour and it is then bed. A gaseous mixtureconsisting of 8.33% by volume left to settle for eight hour-s. The massis dried at 110 C. o p opylene, 8.33% by volume of ammonia and 83.3% fora few hours. The silica impregnated in this way then y Volume of WasPassed Over the catalyst in Such undergoes heating at temperaturecomprised between a q y 35 to attain a Contact tim of 2.5 Sec nds 600 C,and 700 C, for a ti f o 2 up t 30 ho of the mixture itself measured atthe temperature and This permits a reaction to take place within thesilica, p ssure conditions existing n the Catalytic with and throughthis reaction Te and Ce oxides are changed S d c ly in a solid phase toCeTe O in asubstantially quantitative The reaction was carried out atatmospheric pressure extent. The catalyst thus prepared exhibits highcatalytic and at a temperature 0f activity d good selectivity, Theproducts of the reaction analyzed via gas chro- In order to furtherillustrate the present invention g p y displayed the following re ultsCa cu a ed and the advantages thereof, the following specific ex- 0n t eC nv rted propylene: amples are given it being understood that the sameare merely intended to be illustrative and in no wise limita- Net yleldPercent tive Acrylonitrlle 80 The results appearing in the examples havebeen ascergetomtnle tained by means chromatographic analysis of theoutlet i gases of the reactor or by means of quantitative analysis,volumetric and gravimetric, of the condensed products The followingtable shows conditions and data relating and by the analysis of thenon-condensable elements, to Examples 3, 4 and 5, obtained by working,as specified carried out by means of an Orsat apparatus. in Example 2.

TABLE Ratios Percent Percent not yield Air] NHKI Contact Innerconversion Percent Gross Example propylene propylene time, temperaofpropylene Acryloni- Acetonitri- Acrolein HON CO; CO 'eld of No. secondsture,C. trile trile acrylonitrile 3 10 1 2.5 440 65.5 75.8 2 17.7 2.0649.7 4 .do do .110 460 79 70.3 2 22.7 2.5 55.6 5 d0 ..do d0 440 58 76.82 16.4 2.4 44.6

It has been observed that by operating in the same way but in fluid bedaltogether similar results were obtained, while it turned out that thethermal control of the course of the reaction was quite facilitated,especially when operating on an industrial scale.

What is claimed is:

1. A process for the conversion of an olefin selected from the groupconsisting of propylene and isobutylene to acrylonitrile andmethacrylonitrile, respectively, comprising contacting a mixture of thesaid olefin, ammonia and elemental oxygen in the gaseous phase at atemperature of from about 330 C. to about 550 C., with an activecatalyst consisting essentially of CeTe O 2. The process as defined byclaim 1, wherein the ratio of elemental oxygen to olefin in the reactionmixture ranges from between 1:1 to about 3: l, and further wherein theratio of ammonia to olefin in the reaction mixture ranges from betweenabout 0.6:1 to about 2:1.

3. The process as defined by claim 2, wherein the contacting time rangesfrom between about 0.1 second to about 20 seconds.

4. The process as defined by claim 3, wherein the reaction is conductedin fluid bed.

5. The process as defined by claim 3, wherein the reaction is conductedin the presence of an inert diluent.

6. The process as defined by claim 3, wherein the active catalyst isassociated with about 85% to about by weight of a support selected fromthe group consisting of silica, alumina, alundum and fireclay.

7. The process as defined by claim 6, wherein the supe port is silica.

8. The process as defined by claim 3, wherein the contacting time rangesfrom between about 0.5 second to about 15 seconds, at a temperature offrom about 380 C. to about 500 C., and at a pressure of aboutatmospheric.

9. The process as defined by claim 3, wherein propylene is converted toacrylonitrile.

10. The process as defined by claim 3, wherein isobutylene is convertedto methacrylonitrile.

6 References Cited UNITED STATES PATENTS 3,226,421 12/1965 Giordano etal. 260-4653 3,338,952 8/1967 Callahan et a1. 260-4653 JOSEPH P. BRUST,Primary Examiner.

US. Cl. X.R. 252-439 Po-wso' (5/69) UNITmTATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 3,446,833

Dated May 27, 1969 i Enrico Cavaterra, Natale Ferlazzo and Guido PetriniIt is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1, line 43, change 'lose" to loss Column 2, line 1, change"hereafter" to hereinafter Column 4, line 71, after "with" insert fromSififlfil: m

SEAlED a m (SEAL) Attesh mm mull I. I JR. mm calm-sum- 0t Pat-antsAmati-Hg

